Recently, the gut-brain axis has arisen as a major topic of interest in psychiatry. Psychological factors are also thought to play an important role in functional gastrointestinal diseases (FGIDs) and irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD) through “brain-gut interactions”. There is a common comorbidity between gastrointestinal and psychiatric patients, and a large percentage FGIDs are more prevalent in major depressive disorder (MDD) patients. Therefore, we call for the clinical and scientific attention of GI doctors and psychiatrists towards these important topics to enrich our investigation. This special issue aims to publish articles on the related comorbidity studies of gastrointestinal disorders with mental or other physical disorders.